There are a lot of fluffy spells here on the website that do not work. When reading through the spells, please take the time to mull them over to see if they are sensible. Spells that claim powers from Harry Potter, shape-shifting, flying, altering DNA, creating something from nothing, etc are all false and will not work no matter how often or which variation of the spell you do.
But the list of spells is also a great resource, because there is a large selection of non-fluffy spells mixed in. If you did one that was non-fluffy are you sure nothing has happened? The spell may have manifested in a way different to your exact intent. Take time to analyze things that could possibly be the result of the spell, instead of searching for exactly what you had intended.

There are a few simple questions to ask yourself to know if it works
1: Is it humanly possible?
2: Does it defy nature/logic/science?
3: Does this seem like it works?
If the answers to the first and third were yes and the second was no then you're more likely it works